The invention relates to a means of delivering aerosol medication from an MDI canister in a dispenser ("boot") supplied by the manufacturer to a patient, through a hand-held chamber operated by the patient.
MDI drug canisters, which have been used since 1956, are sold with a "boot" that includes an actuator, a nozzle, and a mouthpiece. The patient can self-administer the MDI drug using the boot alone; however, the patient must place the mouthpiece of the boot in or near his/her mouth and inhale exactly when the MDI canister is actuated.
For well over a decade various suppliers have provided valved chambers that can be used in conjunction with an MDI boot. Such valved chambers may improve drug delivery by reducing the oropharyngeal deposition of the aerosol drug and by making the synchronization of actuation of the MDI canister and inhalation of the ejected medication less critical.
The most commonly used valved chamber of this type is marketed under the trademark "AEROCHAMBER", is manufactured by Monaghan Medical Corporation, and refers to U.S. Pat. Nos. 4,470,412 and 5,012,803. Another similar valved chamber of this type is marketed under the trademark "OPTICHAMBER", described in U.S. Pat. 5,385,140 (Smith).
The prior AEROCHAMBER device utilizes only an inhalation valve, and the patient must exhale before placing the device in his/her mouth. That presents a significant problem because it is difficult for many patients to initially perform the required sequence of (1) exhaling, (2) then immediately placing the chamber mouthpiece in his/her mouth, (3) then actuating the MDI canister to inject a medication plume into the valved chamber, (4) then taking a slow deep breath and holding his/her breath for a few seconds. The prior OPTICHAMBER device provides both an inhalation valve and an exhalation valve so that the device need not be removed from the patient's mouth in order to use it. Exhaled air effectively "leaks" around the perimeter of a valve membrane. The valve membrane has cross slits that widen as the patient inhales. A problem with the OPTICHAMBER valved chamber is that it is very inefficient in delivering a medication dose to the patient, because even though the chamber is significantly larger than that of the AEROCHAMBER device, an excessive amount of effort is required for some patients to inhale strongly enough to adequately open the cross slit valve and receive an effective medication dose.
It is very desirable that both the inhalation valve and the exhalation valve of a chamber present very little resistance, especially for infants wherein multiple breaths are needed to inhale an effective dose of MDI medication. It also is important that the dead volume, i.e., the space between the valve seat and the mouth opening, be small so that very little air is re-breathed during the multiple breaths that may be needed by an infant to inhale an effective medication dose.
The prior valved chamber devices include elastomeric boot-adapters into which the mouthpiece of the MDI inhaler is inserted. Such boot-adapters have a radially ribbed structure internal to the valved chamber. When the valved chamber is taken apart for cleaning, it is difficult to remove all water used in cleaning from corners formed by the ribs. Consequently, when the valved chamber is reassembled, the presence of such water creates humidity within the valved chamber. Such humidity tends to prevent medication particles ejected from the MDI canister from becoming completely dry (and hence light in weight), as is necessary for optimum transporting of the medication particles into the lungs of the patient. Another problem is that the prior boot-adapters do not sufficiently maintain the MDI inhaler stable as its canister is actuated by the patient. The MDI inhaler device and nozzle therefore become tilted relative to the valved chamber, ejecting the medication plume directly against an interior wall of the valved chamber, resulting in a major loss of medication particles from the plume.
Thus, there is an unmet need for an improved valved chamber device which avoids the above mentioned problems of the prior art and provides a portable, light, reliable, easy-to-use valved chamber for use with MDI inhalers.